This invention relates to improvements in digital electrical angle-measuring devices of the type comprising a stator having an electrically conductive measuring division conductor mounted on one side thereof, and a rotor having an electrically conductive scanning conductor mounted on one side thereof, wherein the rotor is mounted to move relative to the stator and the division conductor is positioned adjacent to and separated by a gap from the scanning conductor.
Angle-measuring devices of the type described above are known to the art. For example, in West German Pat. No. 2 306 752 there is described a capacitance operated length- or angle-measuring device in which a voltage is applied by means of a fixed electrical contact to the measuring device and an output voltage, which varies as a function of the measurement, is picked up by means of a slip contact. Both the fixed contact and the slip contact are positioned on the outer surfaces of the relatively movable components of the measuring device.
In addition, the corporate brochure "Inductosyn" published by Dr. Johannes Heidenhain GmbH, dated July 1978, discloses inductive angle-measuring devices of several different types, including trailing cable devices suitable for only limited angles of rotation between the rotor and the stator, slip ring devices having external contacting elements as well as external contacting strips, as well as transformer devices having internally located transformers for transmitting the measuring voltage from the rotor to the stator.
Furthermore, in West German DT-AS No. 1 267 433 there is also described an inductive measuring device of the transformer type, in which reference is made to the disadvantage of slip rings and brushes, without specifically specifying these disadvantages.
The disadvantages of slip rings and brushes of the prior art relate particularly to the expensive manner of attachment and installation. Generally brushes and slip rings are mounted externally in prior art measuring devices, an arrangement which requires separate mounting fixtures for either the brushes or the slip rings, thereby increasing the expense of adjustment which is required during the assembly of the measuring device at the place of use. In particular, the brushes or contact members must be positioned accurately with respect to the slip rings for the measuring device to function properly. In addition, because it has in the past been common to mount both the slip rings and the contact members on the outer surfaces of the rotor of the measuring device, it has generally been the case that a greater amount of installation space is required when slip ring type measuring devices are used as compared either with trailing cable or transformer type devices.